The present invention relates to a cutting insert for the chipforming machining of metal workpieces, and in particular to triangular, square, rhombic, rhomboidal or other forms of indexable cutting inserts used with tool holders.
The basic form of such cutting inserts comprises two opposed top and bottom surfaces and a peripheral wall extending therebetween, the cutting edges being formed by the intersection of the top and bottom surfaces and the peripheral wall of the insert. The top surface of the insert is a chip face or a surface which is in contact with the chip formed during the cutting operation. The peripheral wall is a clearance face in relation to the workpiece. The insert can be indexed to place the cutting edges of the top surface successively in an active position. Also, the insert can be inverted so that the bottom surface becomes the top surface and presents a new set of cutting edges.
It is generally desirable that these inserts should have a geometry that will minimize the power required in the metal working operations by controlling the geometry of the chips produced and that the insert chip control geometry should be capable of controlling chips over a wide range of parameters such as depth of cut or feed rate.
SUMMARY OF THE INVENTION
In a broad aspect of the invention, a cutting insert comprises a polygonal body of wear resistant material including opposed top and bottom surfaces and peripheral walls therebetween with cutting edges formed at the intersection between the peripheral walls and at least one of the top and bottom surfaces. A chip breaker groove provided along the cutting edges is constituted by a number of concave depressions, the end depressions of which are disposed adjacent respective corner of the insert. Those end depressions have a length that exceeds the length of intermediate concave depressions disposed between the end depressions. The cutting edge is straight along those end depressions, whereas the cutting edge is wave-shaped along the intermediate depressions as the insert is viewed in side elevation.
In a particular aspect of the invention, a secondary depression is provided in each corner which is defined by a sloping flat surface that extends from the inner margin of a land provided along each edge and extends downwards to a position below the level of a pair of end depressions disposed at that corner. There is also provided a raised elongated rib portion extending along a corner bisector line while being spaced at a distance from the inner end of the secondary corner depression.
In a more particular aspect of the invention there is provided a flat top surface on the raised rib portion along the bisector in each corner whereby the flat tops of the ribs are located in a common horizontal plane that is located above the horizontal plane of a flat land area that extends around each rounded corner region.